Turret assembly

Abstract

A turret assembly for a vessel comprises a moonpool defined in the vessel and a turret structure rotatably mounted in said moonpool. The turret structure comprises a turret table which by means of a main bearing is rotatably mounted in said moonpool and a hollow turret shaft defined by a surrounding shaft wall, which turret shaft has an upper shaft end connected to the turret table, a substantially cylindrical shaft part that extends downwardly from the turret table and a lower shaft end provided with means intended for cooperation with a lower bearing. The shaft wall of the upper shaft end comprises a widened part surrounding the cylindrical shaft part and defines a circumferential crest, wherein the shaft wall of the upper shaft end, starting from said circumferential crest, extends downwardly towards a position where the upper shaft end is connected to the turret table.

The invention claimed is: 
     
       1. A turret assembly for a vessel, comprising a moonpool and a turret structure rotatably mounted in said moonpool, wherein the turret structure comprises a turret table rotatably mounted in said moonpool with a main bearing and a hollow turret shaft defined by a surrounding shaft wall, which turret shaft has an upper shaft end connected to the turret table, a substantially cylindrical shaft part that extends downwardly from the turret table and a lower shaft end cooperating with a lower bearing, wherein the shaft wall of the upper shaft end comprises a widened part surrounding the cylindrical shaft part and defines a circumferential crest, wherein the shaft wall of the upper shaft end, starting from said circumferential crest, extends downwardly towards a position where the upper shaft end is connected to the turret table. 
     
     
       2. The turret assembly according to  claim 1 , wherein the shaft wall of the upper shaft end substantially defines a half torus shape. 
     
     
       3. The turret assembly according to  claim 1 , wherein the shaft wall of the upper shaft end substantially defines a revolved elliptical shape. 
     
     
       4. The turret assembly according to  claim 1 , wherein at least a part of the shaft wall between the circumferential crest and the turret table extends vertically for defining a substantially elongate cylindrical shaft wall part. 
     
     
       5. The turret assembly according to  claim 1 , wherein at least a part of the shaft wall between the circumferential crest and the turret table extends inclined outwardly for defining a widening shaft wall part. 
     
     
       6. The turret assembly according to  claim 1 , wherein at least a part of the shaft wall between the circumferential crest and the turret table extends inclined inwardly for defining a narrowing shaft wall part. 
     
     
       7. The turret assembly according to  claim 1 , wherein the shaft wall, starting from the connection between the cylindrical shaft part and the upper shaft end extends horizontally for defining a ring-shaped circumferential crest. 
     
     
       8. The turret assembly according to  claim 7 , wherein at said ring-shaped circumferential crest a torsion-box construction is provided. 
     
     
       9. The turret assembly according to  claim 7 , wherein at said ring-shaped circumferential crest a solid block is provided. 
     
     
       10. The turret assembly according to  claim 1 , wherein the turret table comprises an upper surface and a lower surface, wherein a channel is provided extending between said upper and lower surfaces, through which channel the turret shaft extends and wherein the circumferential crest of the upper shaft end is located at a level above said upper surface of the turret table. 
     
     
       11. The turret assembly according to  claim 1 , wherein the turret table comprises an upper surface and a lower surface, wherein a recess is provided extending upwardly from the lower surface in which the upper shaft end is located and wherein the circumferential crest of the upper shaft end is located at a level between said upper surface and said lower surface. 
     
     
       12. The turret assembly according to  claim 11 , wherein said recess has a closed upper end below the upper surface. 
     
     
       13. The turret assembly according to  claim 1 , wherein at least part of the shaft wall of the upper shaft end has a larger thickness than remaining parts of the shaft wall. 
     
     
       14. The turret assembly according to  claim 13 , wherein a transition between shaft wall parts with different thicknesses is asymmetrical. 
     
     
       15. The turret assembly according to  claim 13 , wherein the lower shaft end includes a lower table cooperating with the lower bearing. 
     
     
       16. The turret assembly according to  claim 13 , wherein a transition between shaft wall parts with different thicknesses is symmetrical.